230 THE CEINOIDEA CAMEEATA OF NOETH AMEEICA. 



Rhodocrinus Barrisi Hall. 

 Plate XII. Figs. 3, 4^, h, c, d ; and 5a, h, 



1861. Hall; Prelim. Notice of New Spec, of Crin. (Albany), p. 9. 

 1861. Hall; Boston Journ. Nat. Hist., Yol. VII. (No. 2), p. 322. 

 1872. Hall; N. Y. State Mus. Nat. Hist., Bull. 1, Plate 6, Pigs. 16, 17. 

 1881. W. and Sp.; Eevision Paleeocr., Part II., p. 212. 



Syn. Rhodocrinus Barrisi, var. divergens Hall, 1861 ; Boston Journ. Nat. Hist., Vol. VII,, p. 

 324; and N. Y. State Mus., Bull. 1, Plate 6, Pig. 18. 



A very variable species, of the style of Gilhertsocrinus. Calyx forming 

 a polyhedron, with slightly impressed faces and a node at each angle. Dorsal 

 cup broadly truncate at the bottom, widest at the middle of the radials, 

 whence it tapers rapidly and uniformly to the margins of the tegmen, whose 

 diameter is from one third to one half smaller than that of the widest part 

 of the dorsal cup, and less than the diameter at the truncated lower part. 

 Plates highly elevated, their middle portions crowned with spine-like pro- 

 cesses or elongate nodes, connected by well marked ridges, which traverse 

 the sutures and meet with the nodes of adjoining plates. The nodes upon 

 the basals are longer, attaining in very mature specimens a length of four to 

 fiNQ mm. by two mm. wide ; they are directed obliquely downward, while those 

 from the radials, costals, and interradials point horizontally. In less mature 

 specimens, as a rule, the nodes are comparatively smaller. The ridges 

 connecting the basals form around the bottom of the calyx a well defined 

 pentagon, wdth a shallow concavity occupying the whole width of the lower 

 face, enclosing the infrabasals and fully one third of the basals. 



Infrabasals small, but their upper angles visible beyond the column. 

 Basals proportionally large ; their upper half abruptly bent upwards so as 

 to take part in the lateral walls, and forming a sharp edge on which the 

 calyx rests. Eadials a little smaller than the basals. Costals very small ; 

 the first less than one third the size of the radials, but twice as large as the 

 second. Distichals eight to twelve ; the plates of the first row, and some- 

 times those of the second, incorporated into the calyx and in contact later- 

 ally. The free distichals short, cuneate, and in large specimens interlocking ; 

 the upper one axillary, supporting two arms, of which either one or both are 

 branching once again. Arm openings elongate ; arranged in pairs ; directed 

 horizontally. Arms about twice as long as the height of the calyx ; cylin- 

 drical ; somewhat divergent -, the plates sharply cuneate and interlocking. 



